2017 Fiesta Cooling

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Hi all,

Looking for some recommendations on a coolant additive, if any, for my 2017 Fiesta ST. The car overheated under normal conditions last night and I'd like to avoid that as we move into summer. It was 97F out and I headed up a hill on my way home after sitting in stop and go traffic for about 30 minutes. At the top of the hill, the coolant temp light came on (this does not come on unless the coolant gets to 245F if memory serves) and the car went into limp mode.

My first thought is that, while working on the car this weekend, some air got into the system, so I'm going to try to burp and refill as much as I can this evening. After that, as extra insurance, what would folks recommend as an additive to keep temps down, if any? The Fiesta ST has a notoriously poor cooling system and overheats even under normal conditions are fairly common. I have upgraded the intercooler but am not interested in adding an oil cooler or changing out the radiator on a car with 16,000 miles on the clock.

I have historically had good luck with Redline's "Water Wetter," but have read about this not getting along well with and sludging up modern coolants. The coolant in the car is the factory fill Motorcraft "Orange," which I understand is identical to DexCool.

Any thoughts?

Thanks!
 
It should not be overheating, 97 degrees is not that hot.

Is this a warranty item? Something is not working correctly for sure.

Why was the coolant changed on a 2017 car? Vacuum filled?
 
No way it should overheat at 97 degrees, even pulling a grade. Definitely burp the system.

It doesn't surprise me that the Fiesta has an issue with cooling, there's just no room under the hood for airflow.

If I were you, I would look into a software flash that can turn the fans on at a lower temp. It sounds like you heat soaked in traffic, and while going up a hill even with airflow the radiator couldn't remove the excess heat. I doubt it was the grade, itself, that caused it to run hot. It was heat soaked from the previous idle time.

I assume the A/C was blasting the entire time? At close to 100 degrees, I bet the fans are only running 30-40% duty cycle, whereas 50-60% would be better.
 
I used the A/C while sitting in traffic, yeah, but I'm generally not a "blast the AC" guy.

I agree it's likely an air bubble in the system as we had to move the coolant overflow tank to upgrade the passenger's side motor mount and a line may have gotten pinched/temporarily disconnected when we did so, I'm just looking for extra insurance.

And yes, overheating is a very common issue with the Mk7 Fiesta for that exact reason - no room for airflow plus very tiny factory intercooler and radiator.
 
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Hm. Sounds like you've got your bases covered. I doubt moving the coolant tank made a difference, even if a line came disconnected the bubble would have found it's way back up and out fairly quickly.

The problem with using A/C in traffic is that the fan pulls the hot air through both the condenser and radiator and then it just sits under the hood, mixing with heat from the sump, turbo, cat, etc. The thermal load is just too high.

Looks like all you can do is upgrade, or drive less when it's 80+?
 
Yeah, there's an air bleeder valve at the top of the radiator so I'm going to burp it tonight and add coolant if necessary, then check for leaks (I know a lot of the factory fill fluids are underfilled so I might just not have enough coolant).

Good call on the A/C, confirming that my aversion to using it is correct.

Fortunately, I live in Portland where days like this are still pretty rare (though, of course, increasingly common).
 
Maybe you can get a pusher fan (old benz diesels had them) for in front of the radiator that runs off an aftermarket switch/ relay. As said above, you heat soaked it in traffic.

The air bubble idea holds water, too.
 
Originally Posted by gfh77665
I have a 2017 Fiesta, too. Your vehicle should definitely still be under warranty.


You do comprehend that warranties don't come with unlimited miles?
 
Originally Posted by atikovi
Originally Posted by gfh77665
I have a 2017 Fiesta, too. Your vehicle should definitely still be under warranty.


You do comprehend that warranties don't come with unlimited miles?



Uh, yeah.

Given the fact I have bought two new vehicles in the past two years, yes, I think I have very good knowledge of warranties. Most 2 year old vehicles ARE still under warranty, with a few rare exceptions. Thanks so much.
 
An old, cheap trick to get hot air out from under the hood is to unbolt the rear of the hood and stick a couple washers between the hood and the hinges, just enough to open a small air gap. At speed, the airflow will push out the hot air.

But I agree. Should not be having overheating problems being only 2 years old and 97 degrees. Maybe use header wrap and turbo blanket on the exhaust to cut down on underhood temps? It would help turbo spool as well.
 
A friend of mine has one of the three cylinder Fiestas and just had to have the engine rebuilt because the plastic fins on the water pump disintegrated and caused the engine to overheat and warp the head. He bought the extended warranty from Ford and they (of course) denied the claim. He just had to spend thousands of dollars on a car he still owes money on with less than 50,000 miles. Actually, that car has been at Ford about once every few months for some kind of repair.

I'd get rid of that thing as soon as possible and buy a cheap used Civic or Corolla. You should not have to be modifying a new car to make it usable.
 
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See if they have a stant super stat for the fiesta. I have a 13 f150 eco and on stock thermostat I would sit at 205-210 idling and driving. With what we have seen the super stat flows more coolant and opens more consistently at 188 temp. The OEM tstat is 188 as well. With the stant crusing and idling im at 193 and it seems to cool down a lot quicker as well.
 
No WaterWetter with modern OAT coolants. Since you did some potential cooling system work, I would try getting the air out of the cooling system. Seeing that you have a Fiesta ST, you have a turbo to cool down as well.

I'd see if Ford fitted any bleed screws on the engine. Park the car on a slope, nose up or jack it up and open the surge tank cap and let the car run until you have strong heat, fans cycle and no temp warning lights are on. If you have an air compressor, one of these is a good investment to have - it evacuates your cooling system and the vacuum formed will suck in coolant to fill it back up: https://www.amazon.com/UView-550000-Airlift-Cooling-Checker/dp/B0002SRH5G
 
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